Here is the full list of all 11 Kung Fu Er San achievements.
Defeat DAN-LUN
Defeat YANG-SAN
Defeat YIN-LIAO
Defeat XIAO-CHOU
Defeat XUN-FU
Defeat JIAN-TOU
Defeat NAOGUI
Defeat FEN-SHEN
Rescue the boy
Defeat MOSHU-SHI
Finish the game in HARD MODE